Requirement of ERK Activation in Hypoxia Induced Caspase Activation and Apoptosis of Cultured Tubular Cells

Ko, Gang Jee; Lee, Jae Won; Choi, Hye Min; Hyun, Young Youl; Ko, Yoon Sook; Jo, Sang Kyung; Cho, Won Yong; Kim, Hyoung Kyu

Abstract

BACKGOUND: Renal tubular epithelial cells are primary target for hypoxic injury. Hypoxia induced tubular cell apoptosis has been reported previously and thought to be important mechanism of renal dysfunction in ischemic ARF, but precise signaling mechanisms need to be defined. The aim of this study is to clarify intracellular signaling mechanism mediating apoptosis by hypoxic stimuli in cultured tubular cells.
METHODS
HK-2 cells were placed in hypoxic chamber (O2<1%) for 24 hrs in minimal essential medium. DNA fragmentation was detected by Hoechst 33342 stain and FACS. The activation of caspase was measured by fluorometry and activations of p-38, ERK, and JNK were examined by western blot analysis.
RESULTS
Hypoxia induced caspase 3 activation and apoptosis at 24 hrs and this was accompanied by increased phosphorylation of p-38, ERK1/2, and JNK. Pretreatment of p-38 inhibitor (SB 203280) and JNK inhibitor (SP600125) did not afftect the activation of caspase 3 and apoptosis but inhibition of ERK1/2 by PD98059 resulted in partial inhibition of caspase 3 and apoptosis induced by hypoxia.
CONCLUSION
ERK 1/2 activation can be an upstream signal in hypoxia induced caspase 3 activation and apoptosis in tubular cells.